Exhaust pulse control unit

ABSTRACT

An exhaust pulse control unit ( 10 ) for increasing exhaust manifold vacuum in an engine comprises an inlet ( 11 ), an outlet ( 12 ) and an intermediate containment zone ( 13 ). An exhaust pulse capture and expansion zone ( 14 ) is located between the inlet and intermediate zone and a merging zone ( 17 ) between the intermediate zone and the outlet. The capture and expansion zone may consist of two stages with the first stage providing a relatively rapid increase in exhaust gas volume.

[0001] This invention relates to an engine exhaust pulse control unit.In particular, the invention relates to an engine exhaust control unitwhich controls expansion of exhaust gases from an engine to improveengine efficiency.

[0002] In internal combustion engines efficient removal or scavenging ofexhaust gases is desirable from the point of view of engine efficiencyand cleaner burning of fuel to reduce harmful engine emissions.

[0003] Patent specification WO98/23854 discloses a device for optimisingthe efficiency of an internal combustion engine. The device includeseither a fixed or movable means arranged to modify the velocity andpressure of gas flow directed towards a cylinder of the engine orthrough an exhaust pipe for removing exhaust gases from the engine.

[0004] When the device is within the exhaust pipe or system itsintention is to enable the velocity of spent gas to be increased towardsthe free air after the first spontaneous exhaust stage, so creatinggreater vacuum for more efficient engine scavenging.

[0005] The device disclosed in its various embodiments in this earlierpatent specification appears to function as a baffle which restricts theflow of engine exhaust gases and creates turbulent flow of the gases anddoes not appear to function as intended.

[0006] My co-pending Australian patent application PQ2456 (now lapsed)discloses an engine exhaust control unit for increasing exhaust manifoldvacuum in an engine and is an improvement over what is disclosed inWO98/23854.

SUMMARY OF THE INVENTION

[0007] It is an object of the present invention to provide an improvedexhaust pulse control unit and one which may be used as an alternativeto what is disclosed in my co-pending patent application.

[0008] According to one aspect the invention provides an exhaust pulsecontrol unit for creating negative pressure exhaust pulses upstream ofthe unit in a four stroke engine, the unit having a single chamber withan inlet, a separate exhaust pulse expansion and capture zone adjacentthe inlet an intermediate containment zone with the capture andexpansion zone being adjacent one end of the intermediate zone, anoutlet adjacent the other end of the intermediate zone, the outlethaving a greater diameter than the inlet and a merging zone between theintermediate zone and the outlet, wherein an atmospheric return pulseinteracts with an expanded exhaust pulse in the intermediate zone,without the presence of a muffling effect or muffling device in any ofthe zones.

[0009] The intermediate zone is preferably of constant cross sectionalarea for the whole of its length. Exhaust gas pulses enter the unitthrough the inlet and atmospheric pulses enter the unit through theoutlet and the exhaust pulses and atmosphering pulses interact withinthe confines of the intermediate zone.

[0010] The intermediate zone may have a length determined by enginecharacteristics.

[0011] The inlet and the outlet are preferably inlet and outlet tubes.It is preferred that the outlet tube be of a diameter greater than thediameter of the inlet tube and the intermediate zone have a greaterdiameter than the inlet and outlet tubes.

[0012] The capture and expansion zone increase the volume of the gaspassing from the inlet to the outlet. This increase in volume preferablyoccurs in two stages. The first stage provides for relatively rapidincrease in exhaust gas volume and allows exhaust pulses to expand asthey exit from the inlet and progress towards the intermediate zone. Thefirst stage forms a relatively small angle with respect to the inlet.This relatively small angle is smaller than the angle that the secondstage forms with respect to the inlet.

[0013] Preferably the first stage extends at an angle of between 40° to50° relative to a longitudinal axis through the inlet whilst the secondstage extends at an angle between 60° and 80°. Preferably the firststage extends at an angle of 45° whilst the second stage extends at anangle of 60°.

[0014] The exhaust gas pulses are caused to expand rapidly in volume asthey pass from the inlet and into the first stage of the capture andexpansion zone. Further but rapid expansion occurs in the second stage.This causes a boundary layer in the exhaust pulse to expand but acentral portion of the exhaust pulse is not subjected to appreciableexpansion in the second stage. This maintains pulse momentum of thepulses as they travel along the intermediate zone.

[0015] The merging zone is present to ensure that back pressure iscreated to provide for effective scavenging of exhaust from the engineto which the unit of the invention is fitted.

[0016] The merging zone extends at an angle with respect to alongitudinal axis through the outlet. Preferably the angle is between40° and 50°. An angle of 45° is preferred.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] A preferred embodiment of the invention will now be described byway of example with reference to the drawings.

[0018]FIG. 1 shows a longitudinal sectional view of the unit of theinvention;

[0019]FIG. 2 shows a detailed view of the inlet end of the unit of FIG.1;

[0020]FIG. 3 shows a detailed view of the outlet end of the unit of FIG.1;

[0021]FIG. 4 is a graph of horsepower test results;

[0022]FIG. 5 is a graph of torque test results; and,

[0023]FIG. 6 is a graph of power and torque test results.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

[0024]FIGS. 1, 2 and 3 show an exhaust pulse control unit 10. The unit10 has an inlet tube 11 and an outlet tube 12. Tube 12 is of a greaterdiameter than tube 11. Tube 11 is coupled to an engine and receivesexhaust outlet pulses from the engine whilst tube 12 directs exhaustgases to an exhaust outlet at the end of an exhaust pipe.

[0025] The unit 10 has an intermediate zone 13 which extends betweeninlet and outlet tubes 11 and 12. An exhaust pulse capture and expansionzone 14 is located between the inlet tube 11 and the zone 13. The zone14 has a first stage 15 which forms an angle of 45° relative to alongitudinal axis along the tube 11. Zone 14 has a second stage 16immediately adjacent stage 15 and stage 16 forms an angle of 60°relative to the longitudinal axis of the tube 11. Stages 15 and 16 areresponsible for the development of negative pressure through expansionand control of exhaust pulses and provides for more effective scavengingof gases from the engine to which the unit is fitted.

[0026] A merging zone 17 is located between tube 12 and zone 13. Thezone 17 forms an angle of 45° with respect to a longitudinal axis alongtube 12. Zone 17 is responsible for the merging of the outgoing exhaustis pressure pulse with the incoming atmospheric pulse. The length “l” ofzone 13 is dependant on engine specifications.

[0027] The unit of the invention is responsible for creating an increasein power of the engine because it creates low pressure areas betweenexhaust pulses. The unit provides for efficient burning of fuel in theengine and better scavenging of exhaust gases from the engine.

[0028] The exhaust pulse control unit 10 creates negative pressure frompositive pressure generated in an exhaust system of an internalcombustion engine. The unit improves engine efficiency by improvingengine scavenging.

[0029] A series of tests were conducted to illustrate improvements inengine operation of an engine fitting to a vehicle. One set of tests wasconducted without the unit 10 of the invention fitted to the exhaustsystem of the engine and another set of identical tests was conductedwith the unit 10 fitted to the engine of the vehicle. Apart from theaddition of the unit of the invention the engine and vehicles in thetests were identical in all respects.

[0030] The tests were carried out on a computerised chassis dynamometer.Test parameters included atmospheric correction and cold air inductioninto the engine was compensated to 15° C. The vehicle was programmed toan acceleration rate of 50 feet per second per second full throttle.This allowed the vehicle to accelerate through a designated revolutionper minute (RPM) range and plots of power and torque were taken duringthis program at 20 times per second.

[0031] A computerised power loss program was used to interpret torquereadings and a display of tractive effort was obtained at constantacceleration.

[0032] The programmed RPM range covered is affected by thehorsepower/torque difference.

[0033] The graph of FIG. 6 shows plots of power and torque of both testruns (one without a unit 10 and the other with a unit 10 of theinvention) with the vehicle in 3^(rd) and 4^(th) gear over an RPM rangeof 2000 to 5000 RPM. The scale along the bottom of the graph denotesvehicle speed in kilometers per hour (kph), the scale along the lefthand vertical side of the graph relates to power in kilowatts (kw) andthe scale along the right hand side of the graph relates to torque ortractive effort in newtons (N).

[0034] The two traces commencing at about 68 kph and 3000N and extendingsubstantially horizontally across the graph are plots of torque In4^(th) gear starting at 2000 RPM and finishing at 5000 RPM with theupper plot of that pair of plots being with a unit 10 fitted whilst thelower plot of that pair is without a unit 10 fitted to the vehicle undertest.

[0035] The two traces commencing at about 54 kph and 3700N and extendingsubstantially horizontally across the graph are similar plots to thetorque plots just described but with the vehicle being in 3^(rd) gear.The uppermost plot of these two traces is with a unit 10 fitted and thelowermost one is without a unit 10 fitted to the vehicle under test.

[0036] The power traces are also represented in two pairs. One pair ofpower traces with the vehicle in 3^(rd) gear start with the vehicletravelling at about 45 kph and extend at an inclined angle across thegraph and terminate with the vehicle travelling at about 124 kph. Theuppermost trace of this pair is with a unit 10 fitted and the lowermosttrace of that pair is without a unit 10 fitted to the vehicle undertest.

[0037] A similar pair of power plots are present for the test conductedin 4^(th) gear. These two traces commence with the vehicle travelling atabout 68 kph and extend at an inclined angle across the graph andterminate with the vehicle travelling at about 166 kph. The uppermosttrace of the pair is with a unit 10 fitted whilst the lowermost trace ofthe pair is without a unit 10 fitted to the vehicle under test.

[0038] The unit 10 of the invention achieves the following power andtorque improvements over that achieved with a vehicle not fitted withsuch a unit.

[0039] Horsepower

[0040] percentage increase in 3^(rd) gear 2.8% to 5.4%

[0041] percentage increase in 4^(th) gear 3.0% to 9.7%

[0042] Tractive Effort (Torque)

[0043] percentage increase in 3^(rd) gear 2.6% to 4.6%

[0044] percentage increase in 4^(th) gear 3.7% to 9.5%

[0045] Horsepower Output

[0046] percentage increase from 3.9% to 38.3%

[0047] Torque Effort

[0048] percentage increase from 3% to 13.5%

[0049] Highest achieved peak horsepower—seen as high as 125 kw at thewheels over a base line peak horsepower of 116.2 kw.

[0050] The following table summarises the results plotted in FIG. 6.Horsepower Increases are: Speed 3^(rd) Gear 4^(th) Gear  60 kph 5.3%  70kph 5.0% 8.3%  80 kph 5.4% 9.7%  90 kph 2.8% 6.9% 100 kph 3.8% 6.1% 110kph 3.0% 4.0% 120 kph 3.9% 4.7% 130 kph 4.9% 140 kph 4.2% 150 kph 3.9%160 kph 4.8%

[0051] Tractive Effort Increases are: Tractive Effort Increases are:Speed 3^(rd) Gear 4^(th) Gear  60 kph 4.6%  70 kph 4.6% 8.3%  80 kph4.5% 9.5%  90 kph 2.6% 5.6% 100 kph 2.7% 5.9% 110 kph 2.7% 4.4% 120 kph3.6% 3.7% 130 kph 3.9% 140 kph 4.0% 150 kph 4.0% 160 kph 4.6%

[0052] The power/torque output plots shown in FIGS. 4 and 5 wereobtained employing the following test procedure.

[0053] The vehicle was installed into a fully computerised chassisdynamometer and test parameters were verified with atmosphericcorrection and cold air induction compensated to 15° C.

[0054] Power output was achieved by running the vehicle at set RPM lolevels, opening to full throttle whilst being held at that specific RPM.Power output/torque output was logged. The test was conducted at 2000,3000, 4000 and 5000 RPM.

[0055] The plots of FIGS. 4 and 5 are representative of the resultsobtained. The term “base line” refers to the engine without unit 10 ofthe invention fitted whilst the legend “EPU w/stock rear system” refersto the same engine with a unit 10 of the invention fitted to it.

[0056] The following is a summary of the plots in FIGS. 4 and 5.

[0057] Average increase improvements. Horsepower Output @ 2000 RPM  3.9%@ 3000 RPM 23.5% @ 4000 RPM 38.3% @ 5000 RPM 11.3% Torque @ 2000 RPM 3.0% @ 3000 RPM  7.3% @ 4000 RPM  6.1% @ 5000 RPM 13.5%

[0058] The unit of the invention in addition to improvements in powerand torque lead to more fuel efficient operation of the engine andreductions in harmful gas emissions.

1. An exhaust pulse control unit for creating negative pressure exhaustpulses upstream of the unit in a four stroke engine, the unit having asingle chamber with an inlet, a separate exhaust pulse expansion andcapture zone adjacent the inlet an intermediate containment zone withthe capture and expansion zone being adjacent one end of theintermediate zone, an outlet adjacent the other end of the intermediatezone, the outlet having a greater diameter than the inlet and a mergingzone between the intermediate zone and the outlet, wherein anatmospheric return pulse interacts with an expanded exhaust pulse in theintermediate zone, without the presence of a muffling effect or mufflingdevice in any of the zones.
 2. The unit of claim 1 wherein theintermediate zone is of constant transverse cross sectional area for thewhole of its length.
 3. The unit of claim 1 or 2 wherein the inlet andthe outlet are inlet and outlet tubes respectively.
 4. The unit of anyone of claims 1 to 3 wherein the capture and expansion zone consists oftwo stages with the first stage providing a relatively rapid increase inexhaust gas volume.
 5. The unit of claim 4 wherein the first stage formsan angle relative to a longitudinal axis through the unit that is lessthan an angle formed by the second stage.
 6. The unit of claim 5 whereinthe first stage forms an angle of between 40° to 50° relative to thelongitudinal axis and the second stage forms an angle of between 60° to80° relative to the longitudinal axis.
 7. The unit of claim 6 whereinthe first stage forms an angle of 45° to the longitudinal axis and thesecond stage forms an angle of 60° to the longitudinal axis.
 8. The unitof any one of the claims 1 to 7 wherein the merging zone forms an angleof between 40° to 50° to a longitudinal axis through the outlet.
 9. Theunit of claim 8 wherein the merging zone forms an angle of 45° to thelongitudinal axis through the outlet.